1. Field of the Invention
The present invention relates to telecommunication systems and, in particular, to a system in which client access to a prepaid service—i.e. a network-deliverable service which is accessible to a client that has previously deposited currency sufficient to cover the charges for subsequent use of the service into an account of the service provider—is implemented in a general packet radio service (GPRS) system or network.
2. Description of Related Art
The widespread use and popularity of the global system for mobile communication (GSM) has resulted in the development of increasing numbers of new systems for use in digital communications. The central components of the GSM network are the mobile station of a client or network subscriber, the station being identified in the network by means of a subscriber identity module, and the base station, which establishes a radio-based telecommunication connection with the mobile station and determines the cell area within which the mobile station can move without requiring a handover to another cell base station. Such telecommunication network systems are formed of a multiplicity of cell areas. Roaming of a mobile station denotes that the mobile station is visiting or is otherwise located within the area of a telecommunication system of another operator. The subscriber information for a mobile communication system is stored in the home location register (HLR) of that system. It is anticipated that, in the future, the GSM system may perhaps be modified or redeveloped into a universal mobile telecommunications system (UMTS).
In a general packet radio service (GPRS), which has been standardized by the European Telecommunications Standards Institute (ETSI), information is transferred in the form of digital packets. A packet-switched radio service enables the flexible transfer of information to end users using packet-switched protocols, such for example as the Internet Protocol (IP) and X.25 protocol, and is commonly used to transfer information with notable efficiency because the user can define between one and eight time slots for the particular data transfer.
To implement packet-switched radio service in the global system for mobile communication, two new network nodes, among other things, are needed. A serving GPRS support node (SGSN) monitors the locations of individual mobile stations and implements security operations and access control. A gateway GPRS support node (GGSN) connected to the serving GPRS support node implements the telecommunication connection to external packet-switched telecommunication networks. Also required is the registration information for the subscribers belonging to the access network in the home location register.
Development of the so-called wireless application protocol (WAP) now permits Internet services to be brought into wireless mobile stations. The WAP protocol enables the connection setup from a mobile station to the Internet to be defined so as to allow access to a World Wide Web browser program, an e-mail program and other Internet applications using the mobile station. Other so-called micro-browser programs, such for example Imode over GPRS and Compact HTML over GPRS, have also been developed.
Currently known is the so-called Customized Applications for Mobile network Enhanced (CAMEL), with which a network operator can implement services accessible to a subscriber of the network who is visiting a telecommunication network of another operator. CAMEL has for example been presented in the standard TS 22.078 V.3.2.0 (1999-12) of the 3rd generation partnership project (3GPP).
It is also known to implement services in telecommunication networks by means of so-called intelligent networks. An intelligent network (IN) is a telephone network system in which the logic needed to implement services has been placed in a separate unit. Since that unit need not necessarily be located in the telephone exchange, it is possible to advantageously add and develop new services without having to re-plan or reconstruct the central equipment of the network. Such a system typically comprises several nodes, one of which is the service control point (SCP).
A typical service provided in an intelligent network is a prepaid service, in which the subscriber first deposits a certain amount of currency into the account of the service provider and is then able to thereafter use the service. The subscriber is charged for each use of the service by deducting the current charges from the currency already in the account. If no or insufficient currency remains in the account of the subscriber, then the subscriber cannot use the service; only when the subscriber has deposited additional currency into the account, as via a telephone number against which charges may be assessed, can the subscriber then re-call or reaccess the service. Often, the billing criteria by which currency amounts are debited from the subscriber's account is based on time or on the amount of information transferred.
Credits may also be used in lieu of debiting an existing account into which currency has previously been deposited. In the use of credits, the subscriber purchases from the operator connection time on credit, with respect to which a set of credits and an entry in the database of the service provider are stored. The value of one credit may be, for example, one minute of connection time. When the client utilizes the service, the appropriate number of credits stored in the database are deducted in accordance with a predetermined debiting criterion.
Implementation of a prepaid service in a packet-switched radio service network, however, remains a problem. Implementation of a service requires the use of circuit-switched components in a packet-switched radio service network, which is both costly and cumbersome.
It is known to implement a debiting service in a mobile communication network by enhancement of customized applications (CAMEL). This requires that the interface of the intelligent network, which is able to communicate with the service control point (SCP) of the intelligent network, be added to the serving GPRS support node. Such an arrangement is, however, complicated as compared to the transmission of messages in accordance with the present invention, and expressly requires the addition to the network of another and essential component. At present, not a single device manufacturer has provided implementations of a first phase packet-switched radio service network that supports the CAMEL solution. Furthermore, in mobile station roaming CAMEL would require that the serving GPRS support node (SGSN) of each operator that is part of the mobile station roaming contract must support the particular CAMEL functionality in question. For the time being, this seems unlikely to be or become the case in the near future.
FIG. 1 depicts an illustrative prior-art signaling diagram which depicts the transmission of messages between the components of a telecommunication network MCN. The components shown in FIG. 1 are a mobile station MS, a serving GPRS support node SGSN, and a gateway GPRS support node GGSN. Mobile station MS first sends a request for service activation to the serving GPRS support node SGSN, which through security operations checks the authenticity of the information of mobile station MS. Next, a request for telecommunication connection setup is sent from the serving GPRS support node SGSN to the gateway GPRS support node GGSN. When the telecommunication connection has been set up, a message so indicating is sent to the serving GPRS support node SGSN, from which a response is further transmitted to mobile station MS.